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It is a filter topology named allpass or all-pass. If all your frequencies are fixed, once and for all MAYBE and a very big emphasize on maybe. You can use allpass filters to tune the signals into equal phase. However this is not something I even remotly have done my self. What I would have done. Is to use the most out of phase signal as a reference, and then tried to tune the rest of the 11 signals into this phase with allpass filters, although this would probably require multiturn pots. And will also require a lot of tuning work. Once again this is just an idea from the top of my head

I will not use DDS because the project requires 12 channels to be synchronized  and 3pcs 4 channel DDS makes the project very expensive.
The idea is to filter 12 synchronize square waves (8 order switched caps + 1pc LPF to attenuate the clock - clock ratio to rolloff is 100) and transform them in sine wave.

Thanks Optikon for your answer,

The LPF is used to attenuate the clock of an high order switching capacitor filter (generate variable frequency, crystal controlled sine wave from square wave); I can compensate for phase in digital domain but the application is multichannel, so it's very difficult to replicate the same analog filter on each channel due to the components tolerance. Also, a multichannel DDS gets too expensive.

Anyway, I'll try to push higher as much as I can the rolloff frequency...

Thanks and most appreciate your suggestions.
-an

If you can use LTspice or other spice sim, you can try an ideal square wave clock fed to a single pole LPF.

You can then try push pole location according to

1) High as possible until you do not get enough clock attenuation.
2) Low as possible until you see too much phase at 120Hz

If you can do more than 1 order, it helps. butterworth or other types can give very strong attenuation roll offs

[W]

This is a small but useful extension for the 3-alarm clock (see my post #35 and #36).
The circuit (and its handling) remained unchanged, only the name (and operation) of the 3 alarms were modified as follows:

- W alarm (on Working days only, Monday through Friday)
- R alarm (on Rest days, Saturdays and Sundays only)
- A alarm (simple daily Alert, same as the alarm C in post #36 above)

  The pre-set (but adjustable) alarm times (at start all three are off):
w 07:00 (hour:minute, lowercase 'w' = disabled)
r  07:30
a 08:00 (usually this is not used ie remains off)

  Of course, the distinction between work days and rest days only works properly if the RTC time and date is set correctly on the first power-up.

  To try it, simply use the supplied new HEX, either in the Proteus simulation (using the DSN attached to my post #36), or in the real circuit, after re-burn the PIC.

Best regards,
zuisti

In case you need a set of identical RC filters, adding R-trimmer is not very difficult though requires some extra work.
Still do not get it clear. Do you suppose to use multichannel DDS or not? If DDS single when thing becomes multichannel?

Thanks Optikon for your answer,

The LPF is used to attenuate the clock of an high order switching capacitor filter (generate variable frequency, crystal controlled sine wave from square wave); I can compensate for phase in digital domain but the application is multichannel, so it's very difficult to replicate the same analog filter on each channel due to the components tolerance. Also, a multichannel DDS gets too expensive.

Anyway, I'll try to push higher as much as I can the rolloff frequency...

Thanks and most appreciate your suggestions.
-an

Hi All,

I need an analog 1'st order low pass filter with frequency corner at 2KHz and with 0deg phase shifting for frequencies up to 120Hz. Any idea of implementation?

Thanks,
-an

As stated, your requirements cant be met (analog filter)

You can have a very high order LPF design at 2kHz and have "small" (not zero!) phase at 120Hz

*OR*

You can have a single order filter but you will have push the cutoff frequency much higher frequency (> 2kHz)  to achieve very small phase at 120 Hz

You can eliminate the concept of a zero phase shift right now, its non causal and not physically realizable. You can however, design to an arbitrarily small phase.

Once you mention one of these tradoffs, a good suggestion can be made.

Hi All,

I need an analog 1'st order low pass filter with frequency corner at 2KHz and with 0deg phase shifting for frequencies up to 120Hz. Any idea of implementation?

Thanks,
-an

Do you want this to be done in an analog or digital setting. Also what are you trying to achieve?

Hi All,

I need an analog 1'st order low pass filter with frequency corner at 2KHz and with 0deg phase shifting for frequencies up to 120Hz. Any idea of implementation?

Thanks,
-an

https://www.espressif.com/sites/default/files/documentation/ESP32_FAQs__EN.pdf

5.3. Coexistence

5.3.1. How do ESP32 Bluetooth dual modes coexist? And how to use dual-mode
Bluetooth?

ESP32 BT&BLE dual-mode Bluetooth is very easy to use. It does not require any special
configuration or calling functions. As a developer, all you have to know is (1) BLE calls the
BLE APIs, and (2) Classic Bluetooth calls the Classic Bluetooth APIs. For details, please
refer to ESP32 BT&BLE Dual-mode Bluetooth.

5.3.2. How do ESP32 Bluetooth and Wi-Fi coexist?

In the menuconfig menu, there is a special option called “Software controls WiFi/
Bluetooth coexistence”, which is used to control the ESP32's Bluetooth and Wi-Fi
coexistence using software, thus balancing the coexistence requirement for controlling the
RF module by both the Wi-Fi and Bluetooth modules. Please note that if Option “Software
controls WiFi/Bluetooth coexistence” is enabled, the BLE scan interval shall not exceed
0x100 slots (about 160 ms).

• If only the BLE and Wi-Fi coexistence is required, this option can be enabled or
disabled. However, if this option is not enabled, please note that the “BLE scan
interval - BLE scan window” should be larger than 150 ms, and the BLE scan interval
should be less than 500 ms.
• If the Classic Bluetooth and Wi-Fi coexistence is required, it is recommended that you
enable this option.

In ESP-IDF V3.0 and earlier versions, the performance of Classic Bluetooth and Wi-Fi
coexistence might be poor at times. However, in ESP-IDF V3.1 and later versions, we has
solved this issue. At the moment, ESP32 can simultaneously function as a Wi-Fi module
and as a Bluetooth speaker, playing music smoothly.

According to this information, you should check ESP-IDF version to be V3.1 or later. If it's lower, then better to give up or upgrade.